Links between deglaciation and magmatism have long been hypothesised, particularly on divergent plate boundaries. But what happens along convergent margins when ice is suddenly removed from the landscape? What is the effect of unloading on magma chamber evolution? We don't know, and perhaps the impact is negligible, yet the question is a cool one and increasingly important as our planet warms and the glaciers mantling active volcanoes continue to shrink. This research, which is very much in its early stages, combines geomorphology and geochemistry to explore the impact of deglaciation on the internal workings of volcanic systems in the Pacific Ring of Fire. Thus far, my focus has been primarily on establishing eruption chronologies with cosmogenic nuclides (helium-3 in pyroxenes).
ESRL 2022 Short Call, Fire and Ice: Potential magmatic and glacial-geomorphic constraints on the role of deglaciation in magma chamber evolution
Gordon Bromley and Michael Stock (PIs), Marty Yates (UMaine collaborator)
This project combines mineralogic and cosmogenic geochronologic data from the Central Volcanic Zone of South America to help resolve potential relationships between rapid deglaciation and magma-chamber behaviour and magma production. Focusing on high-relief Quaternary stratovolcanoes (Coropuna, Ampato, Sabancaya) with directly dated glacial chronologies, we are using Zetium WD-XRF analysis of glacial- and postglacial-age lavas (dated with cosmogenic helium-3 surface-exposure dating), in conjunction with electron microprobe analysis, to evaluate the pressure-dependent partitioning of trace elements into minerals under conditions of full glacial loading and unloading. This project is part of our larger, collaborative programme involving Peru’s Observatorio Vulcanológico de INGEMMET.
Bromley et al., 2019. In situ cosmogenic 3He and 36Cl and radiocarbon dating of volcanic deposits refine the Pleistocene and Holocene eruption chronology of SW Peru. Bulletin of Volcanology 81, 64. https://link.springer.com/article/10.1007/s00445-019-1325-6